Experiments have been designed to elucidate the structure of animal cell membranes. The studies focus on the asymmetric nature of the two monolayers of membrane bilayer. To elicit the kinds of information needed to describe the fine structure of each monolayer, membrane-enveloped viruses and phagocytized latex beads (phagosomes) are used as sources of right-side out and inside out plasma membranes for ESR spin-labeling studies and for protein mapping studies. Other systems being examined concurrently include Racker vesicles containing phage M13 coat protein and whole cell systems, e.g., murine B- and T-lymphocytes. Carbohydrate derivatives of fatty acid spin labels are being exploited to preferentially monitor the physical properties of the individual monolayers of sealed membrane samples, while carbohydrate derivatives of fatty acids which contain photoactivatible azido groups are being used to analyze the architectural features of each monolayer. The immediate goal of the project is to examine the basis and role of vertical physical asymmetry in biological membranes with particular emphasis on the transverse disposition and dynamics of membrane components. BIBLIOGRAPHIC REFERENCES: Wisnieski, B.J., and K.K. Iwata. ESR evidence for vertical asymmetry in animal cell membranes. In press. Biochemistry (1977). Wisnieski, B.J., K.K. Iwata, C.M. Manweiler, and J. Bramhall. Synthesis and characterization of photactivatible probes for high resolution mapping of membrane proteins. ICN-UCLA Symposia on Molecular and Cellular Biology: Molecular Aspects of Membrane Transport (1977), to be published.